1. Field of the Invention
The present invention relates to imaging systems and more particularly to thermal imaging systems for military applications.
2. Description of the Related Art
There is an ever increasing demand for robust performance from infrared (IR) sensors for military applications. Range of detection and range of recognition, for example, are two critical performance parameters for a tank operating in a terrain with long ranges of open space, e.g., a desert environment. A conventional IR imaging system for a typical tank provides for three to 10 times magnification. Typically this magnification is provided in two fields of view, with each field of view being the angular extent of an area viewable by the sensor.
With a single optical arrangement, an increase in the range of magnification necessarily limits the field of view. In addition, resolution is limited in such a system as the magnification increases.
The importance of high optical performance and the cost of tanks and other military vehicles mandate a retrofit of existing vehicles. However, a practical problem facing the manufacturer of a thermal imaging system is that any new system must conform within the aperture and dimensionality constraints or "form factor" of the vehicles. This problem has been addressed by the use of a multiple field of view optical arrangement by which different sets of lens are substituted within the housing depending on the desired range or field of view.
Unfortunately, this requires the user to manually replace one set of lenses with the other and also possibly requires the manual focusing (compensation) thereof.
Accordingly, what is needed is an improved thermal imaging system that affords various powers of magnification and fields of view within conventional form factor constraints which has an automatic focus compensation.